1. Technical Field
The present invention relates to a method of adjusting a frequency of a resonation device and a method of manufacturing a resonation device.
2. Related Art
As a resonation device which is used in a reference frequency signal source of a communication instrument, a measurement instrument, or the like, a quartz crystal oscillator is known. In general, the quartz crystal oscillator requires a stable output frequency with high accuracy. In the quartz crystal oscillator, for example, a quartz crystal resonator element and a circuit for oscillating the quartz crystal resonator element are arranged in a case, and in order to stabilize the output frequency with high accuracy, it is necessary to perform the frequency adjustment of the quartz crystal resonator element.
For example, JP-A-2008-91970 discloses a method which performs the frequency adjustment of a piezoelectric resonator element (piezoelectric resonator element) arranged on a chip substrate with an IC circuit formed thereon.
JP-T-9-503361 discloses a method which performs the frequency adjustment of a resonator element for use in a temperature-compensated quartz crystal oscillator (TCXO) in a state where a temperature compensation circuit is operated in a normal manner. In the method disclosed in JP-T-9-503361, it is possible to perform the frequency adjustment of the resonator element in a state where the temperature compensation circuit is operated in the same manner as in an actual operation.
As the quartz crystal oscillator, in addition to the above-described examples, an oven controlled quartz crystal oscillator (OCXO) in which extremely high frequency stability is obtained is known. The OCXO generally includes a thermostat oven which is temperature-controlled by a heating element or the like so as to be maintained at a given temperature (for example, 85° C.) higher than a normal temperature (for example, 25° C.), and a quartz crystal resonator element is housed in the thermostat oven. In general, the frequency adjustment of the quartz crystal resonator element is made in a normal temperature atmosphere, or the frequency adjustment is performed in a state where the quartz crystal resonator element is held in the housing at a normal temperature.
However, in case of a resonation device, such as an OCXO, there may be a difference in environment state, for example, a difference in operation state of a circuit of a resonation device during frequency adjustment and in a state where a heating element is being driven (a state where the heating element is operated and the resonation device is used as an oscillator, that is, an actual use state), or a difference in temperature of the quartz crystal resonator element. With this, for example, since there is a difference in frequency of the quartz crystal resonator element during frequency adjustment and in a state where the heating element is being driven, there may be a large difference in frequency, at which frequency-temperature characteristics become a maximum value and a minimum value, between individual OCXOs. For this reason, even if the heating temperature of the heating element is set based on the result of the frequency adjustment of the quartz crystal resonator element such that desired frequency accuracy is obtained, required frequency accuracy may not be obtained.
In this case, for example, although it is necessary to adjust the heating conditions of the heating element for each individual OCXO, when there is large deviation in frequency-temperature characteristics of each individual OCXO, an operation to perform a setting so as to change the heating conditions for each individual OCXO should be performed, and production efficiency may be degraded.